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Neuroscience > Cerebellum/Basal Ganglia > Flashcards

Cerebellum/Basal Ganglia Flashcards

1
Q

Cerebellum

A
  • plans for coordinated movements, adjusts movements, and non-motor functions
  • it does not have direct connection to motor neurons
  • after cerebellar damage there is NO muscle paralysis or sensory deficits
  • Feedback mechanism: receives info from ongoing movements and makes adjustments (adjustor of movements)
  • Feedforward mechanism: predicts consequences of motor commands from past experience (comparer of movements) and depending on match/mismatch re-calibrates for future purposes (calibrator of movements)
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2
Q

Flow of information into cerebellum

A
  • receives info from motor planning & execution areas from cerebral cortex
  • receives sensory feedback info from somatosensory, vestibular, visual, & auditory receptors
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3
Q

Parts of the cerebellum

A
  • Flocculonodular lobe (bottom portion near pons) = vestibulocerebellum
  • Vermis and Paravermis (top portion near pons) = Spinocerebellum
  • Lateral hemisphere (large portion forming point away from pons) = Cerebrocerebellum
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4
Q

Flow of information through the circuitry inside the cerebellum

A
  • all inputs to cerebellum via climbing & mossy fibers
  • climbing fibers go to 3 deep cerebellar nuclei & purkinji fibers
  • mossy fibers go to granule cells & purkinji cells via parallel fibers
  • all output via purkinji cells back to cerebellar nuclei
  • out of cerebellum to cerebral cortex/brainstem nuclei
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5
Q

Vestibulocerebellum

A
  • receives inputs from vestibular system
  • outputs back to vestibular nuclei
  • efferents from vestibular nuclei regulate VOR centrally to control eye movements & to control neck/trunk axial muscles to influence postural control
  • maintaining VOR and balance are the main functions
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6
Q

Spinocerebellum

A
  • helps execute coordinated movements using both feedforward and feedback mechanisms
  • inputs from spinal cord via 4 spinocerebellar pathways
  • receives sensory inputs from visual, auditory, & vestibular systems
  • outputs adjust motor activity by influencing medial tracts (posture/tone) and lateral tracts (fine movements) by sending projections from fastigial and IP nuclei to brainstem nuclei & by influencing cerebral cortex via thalamus indirectly
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7
Q

Cerebrocerebellum

A
  • involved in planning for coordinated movements
  • uses feedforward mechanism
  • connections form a loop between the lateral cerebellar hemisphere & cerebral cortex: cerebro-cerebello-cerebral loop
  • receives direct inputs from pontine nuclei & gives off direct outputs to thalamus
  • involved with motor & cognitive learning
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8
Q

Signs of cerebellar dysfunction

A
  • problems with eye movements: nystagmus
  • Disequilibrium: loss of balance
  • Uncoordinated movements: dysmetria (over/under shooting a movement), ataxia, dyssynergia (inability/desynchronization of movements)
  • unilateral cerebellar lesions cause impairments on the same side of body: spinocerebellar afferents are ipsilateral & cerebellar efferents project to contralateral cerebral cortex
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9
Q

Lesions in vestibulocerebellum

A
  • nystagmus
  • difficulty maintaining sitting/standing balance (truncal ataxia)
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10
Q

Lesions in spiinocerebellum

A
  • limb incoordination (DDK, dysmetria)
  • ataxic gait (wide based unsteady gait)
  • action/intension tremor
  • dysarthria
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11
Q

Lesions in cerebrocerebellum

A
  • difficulty in planning complex movements (mostly fine motor)
  • difficulty with motor areas for playing instruments, fasten buttons, typing on keyboard
  • disruption of timing of joint movements (decomposition of movements - dyssnergia)
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12
Q

Parts of the basal ganglia

A
  • 5 nuclei: Caudate, Putamen, Globus Pallidus, Subthalamic nucleus, Substantia nugra
  • Striatum = Caudate and Putamen
  • C-shaped Caudate wraps around the Thalamus
  • Lentiform Nucleus = Putamen and Globus Pallidus
  • Substantia nigra = compacta & reticularis
  • Globus Pallidus = externus and internus
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13
Q

Basal ganglia functions

A
  • plans & executes coordinated motor activity but does NOT have direct connections to motor neurons
  • involved in movement control for goal-directed behavior & helps in judging/decision making by taking into account socially appropriate/inappropriate situations & emotions
    -for influencing motor control the basal ganglia regulates the level of inhibition in various motor pathways
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14
Q

Basal agnails circuitry

A
  • inputs enter caudate/putamen from cerebral cortex
  • outputs exit through Globus Pallidus internus/Substantia nigra to the thalamus
  • Loops: goal-directed behavior loop, social behavior loop, emotion loop, oculomotor loop, and motor loop
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15
Q

Goal-directed behavior loop

A
  • example: deciding whether to run a yellow light when running late to work
  • lesion in bilateral caudate = inattention, distractibility, poor concentration, NO movement disorders
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16
Q

Social behavior loop

A
  • example: deciding whether to run a yellow light with grandma sitting beside you
  • lesion in bilateral caudate head = prone to frustration, hyper sexual, shoplifting, violent, NO movement disorders
17
Q

Emotional behavior/Limbic circuit loop

A
  • example: involved with emotional & reward/pleasure seeking behavior, links emotions & motor systems
  • lesion in ventral striatum = depression, emotional blunting “mask-like” facial expression
18
Q

Oculomotor circuit loop

A
  • example: to decide whether to use fast eye movements (saccades) to direct attention to visual objects of interest
  • lesions in basal ganglia can cause impaired saccades
19
Q

Motor circuit loop

A
  • regulates movements by indirectly controlling activity in voluntary muscles, postural muscles, & CPG
  • this loop up or down regulates activity in various motor tracts to promote desired movements & inhibit undesired ones
20
Q

Influence of basal ganglia on motor pathways

A
  • output of motor circuits is always inhibitory on the motor pathways
  • regulates activity of motor thalamus & some other brainstem motor nuclei by having inhibitory influence
  • (1) Motor thalamus –> lateral corticospinal & rubrospinal tracts –> MNs to muscles for voluntary movements
  • (2) Pedunculopontine nucleus –> reticulospinal tracts –> MNs to postural & girdle muscles
  • (3) Midbrain locomotor region –> reticulospinal tracts –> stepping pattern generators (walking)
  • output influences voluntary movements, postural & girdle movements, and gait
21
Q

Go/Direct pathway

A
  • facilitates desired movements by disinhibiting thalamus due to increased inhibitory activity of striatum on Globus Pallidus internus
  • substantia nigra has fine tuning effect on striatum
  • Globus Pallidus internus has the leash to thalamus activity
22
Q

No-go/Indirect pathway

A
  • suppresses unwanted movements by inhibiting thalamus due to increased inhibitory activity of striatum on Globus Pallidus externus
23
Q

Hyperdirect pathway

A
  • purpose is to inhibit all ongoing movements before initiating voluntary movement
  • motor cortex sends strong excitatory inputs to sub thalamic nucleus which excites globs pallid us internus which in turn inhibits thalamus
24
Q

What does normal movement need in the 3 pathways

A
  • needs optimal levels of activity in all 3 pathways to promote desired movements & suppress unwanted movements
  • optimization between different pathways brought about by the fine tuning by substantia nigra using dopamine
25
Q

What if tuning starts to malfunction

A
  • If the direct pathway becomes less active - may cause lack/slowness of desired movements, ex: bradykinesia
  • If the indirect pathway becomes less active - may cause increase in unwanted movements, ex: dyskinesia, chorea, & ballismus
26
Q

Parkinson’s disease

A
  • bradykinesia
  • freezing of gait
  • tremor
  • rigidity - cogwheel type
  • non-motor signs: mask like facial expression, depression, psychosis, or dementia

Neuroscience (10 decks)

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